Azithromycin, which is also named 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A, exists in a dihydrate form as well as in numerous non-dihydrate forms.
Azithromycin is administered for the treatment of various infections, particularly infections of the urinary tract, bronchial tract, lungs, sinuses and the middle ear.
In treating pediatric patients, azithromycin is administered in the dosage form of an oral suspension which is administered through a single or multiple dose course of therapy. The oral suspension dosage form is preferred for pediatric therapeutic use, as it provides better control of the amount of azithromycin administered and as many pediatric patients cannot swallow other oral dosage forms. However, due to azithromycin's extremely bitter taste, suitable flavoring is required to ensure patient compliance and to reduce emesis after swallowing. To date, the oral suspensions of azithromycin comprise azithromycin dihydrate and a combination of banana, cherry and vanilla flavorings which are used to mask the bitter taste of the azithromycin.
Presently, the use of non-dihydrate azithromycin oral suspensions is contemplated. Non-dihydrate azithromycin also has an extremely bitter taste. Due to this bitter taste, these non-dihydrate azithromycin oral suspensions will also require suitable flavoring or sweetening agents to mask the bitter taste and ensure patient compliance. Unfortunately, forms of non-dihydrate azithromycin, when in many flavored oral suspensions, are not stable and often rapidly convert to other forms of azithromycin. No conversion is exhibited by azithromycin dihydrate in flavored oral suspensions.
Conversion from one form of azithromycin to another is undesirable as the subsequent azithromycin forms may not be bioequivalent to the initial azithromycin form. This potential change in bioequivalence, due to azithromycin form conversion, could result in administering an underdose or overdose of azithromycin to a patient, which is particularly significant for pediatric patients who require tighter dosing regimens.
Thus, as form conversion is not a desirable characteristic of a pharmaceutical formulation, what is needed is a means for stabilizing non-dihydrate azithromycin in an oral suspension to reduce the rate of form conversion.